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Y. Hisada et al.
have shown that increased levels of thrombin lead to the generation of denser fibrin with thinner fibers.44
Effect of neutrophil depletion on thrombus size in mice bearing human pancreatic tumors
Thrombi in the group of tumor-bearing mice treated with IgG weighed significantly more than those in con- trols [controls vs. tumor-bearing mice (median [range]): 16.4 [13.8-22.4] g vs. 31.9 [29.1-36.5] g; P<0.001, n=4-5]. Next, we investigated the role of neutrophils in thrombus formation in tumor-bearing mice and control mice by depleting neutrophils using the anti-Ly6G antibody 1A8. Administration of 1A8 significantly decreased levels of cir- culating neutrophils in both control mice [IgG vs. 1A8 (median [range]): 2.9 [1.9-4.4] x 103/mL vs. 0.3 [0.2-1.3] x 103/mL; P<0.05, n=4-5] and mice bearing human pancreatic tumors [IgG vs. 1A8 (median [range]): 6.7 [3.8-8.5] x 103/mL vs. 1.1 [1.0-3.7] x 103/mL; P<0.05, n=4-5]. Depletion of neu- trophils decreased thrombus weight in tumor-bearing mice but not in control mice (Figure 5).
Effect of DNase I administration on thrombus size in mice bearing human pancreatic tumors
Thrombus weight was significantly increased in the vehi- cle treatment group of tumor-bearing mice compared with that of control mice [controls vs. tumor-bearing mice (medi- an [range]): 15.7 [12.1-25.2] g vs. 27.25 [22.8-47.8] g; P<0.05, n=5-6]. We determined the effect of DNase I administration on the size of thrombi in mice bearing human pancreatic tumors. DNase I degrades both cfDNA and NET. We found that administration of DNase I significantly reduced throm- bus weight in tumor-bearing mice but did not affect throm- bus weight in control mice (Figure 6).
Discussion
We observed a striking increase in neutrophils in the cir- culation of nude mice bearing human pancreatic tumors compared with controls. In addition, we found increased levels of plasma biomarkers that either increase neutrophil
AB
Figure 4. Analysis of thrombi by scanning electron microscopy. (A, B) The red blood cell (RBC) and fibrin content in thrombi from control and tumor-bearing mice were assessed by scanning electron microscopy using a SEM EVO40 (Carl Zeiss GmbH, Oberkochen, Germany). Upper panels are representative images of thrombi from control and tumor-bearing mice. RBC occupancy was quantified in five to seven randomly selected images from each animal (A, data from each thrombus are shown with the same color in the lower panel). The diameter of 300 fibrin fibers from separate parts of each thrombus was measured (B, every 10th measured value is plotted in the same color for each thrombus in the lower panel). Lines indicate the median values of the bottom, median and top quartiles calculated from the data of six animals from each group (shown in different colors) based on 35 images in the control group and 32 images in the tumor group. The statistical analysis was performed using 35 or 32 input data for RBC occupancy and 1,800 data for fiber diameter according to the two-step procedure described in the Online Supplement (Bootstrap Kuiper test P<0.001 for all three quartiles of the datasets in the lower panels).
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haematologica | 2020; 105(1)